Pulse oximetry is a continuous and non-invasive method of measuring the level of arterial oxygen saturation in blood. The measurement is taken by placing a sensor on a patient, usually on the fingertip for adults and the hand or foot for neonates. The sensor is connected to a pulse oximetry instrument with a patient cable. The sensor collects signal data from the patient and sends it to the instrument. A pulse oximetry instrument typically displays the calculated data as a percent value for arterial oxygen saturation (SpO2), as a pulse rate (PR) and as a plethysmographic waveform.
Pulse oximetry is governed by a several principles. Oxyhemoglobin (oxygenated blood) and deoxyhemoglobin (non-oxygenated blood) differ in their absorption of red and infrared light (spectrophotometry). Also, the amount of arterial blood in tissue changes with an arterial pulse (photoplethysography). Therefore, the amount of light absorbed by the varying quantities of arterial blood changes as well.
A typical pulse oximeter uses a two-wavelength pulsatile system to distinguish between oxygenated and deoxygenated blood. Signal data is obtained by passing red and infrared light through a capillary bed (for example a fingertip, a hand, a foot) and measuring changes in light absorption during the pulsatile cycle. A typical pulse oximeter utilizes a sensor with red and infrared light-emitting diodes (LEDs) that pass light through the site to a photodiode (photodetector). The photodetector receives the light, converts it into an electronic signal and sends it, via a patient cable, to the pulse oximeter for calculation.
A pulse oximeter measures and displays functional saturation, which is the amount of oxygenated hemoglobin expressed as a percentage of the hemoglobin that can transport oxygen. This is not a measure of fractional saturation, i.e. oxygenated hemoglobin expressed as a percentage of all measured hemoglobin, including measured dysfunctional hemoglobin such as carboxyhemoglobin or methemoglobin.
Oxygen saturation measurements obtained from a pulse oximeter are commonly compared to saturations calculated from the partial pressure of oxygen (PO2) obtained from an arterial blood gas sample. The calculated value obtained from the blood gas sample, however, may differ from the SpO2 measurement of the pulse oximeter. Different results are usually obtained from the blood gas sample if the calculated saturation is not appropriately corrected for the effects of variables that shift the relationship between PO2 and saturation, such as pH, temperature, the partial pressure of carbon dioxide (PCO2), and fetal hemoglobin. Also, as blood gas samples are usually taken over a period of 20 seconds (the time it takes to draw blood) a meaningful comparison can only be achieved if the core oxygen saturation of the patient is stable and not changing over the period of time that the blood gas sample is taken.
Embodiments of the present invention seeks to overcome some or al of these and other problems.
One aspect of a pulse oximetry user interface is a display and a plurality of views each configured to occupy at least a portion of the display. Each of the views are adapted to present data responsive to a physiological signal. A plurality of icons are configured to occupy a portion of the views and adapted to designate the content of the views. Further, a plurality of keys are proximate to the display and are associated with or otherwise correspond to the icons such that selection of key corresponds to selection of an icon. One of the views is a pleth view that presents a pulse waveform. Another one of the views is a trend view that presents a trend graph. At least one of the icons can be selected so as to switch the display between the pleth view and the trend view.
Another aspect of a pulse oximetry user interface is a method comprising the steps of deriving a pulse waveform responsive to a physiological signal, calculating a data trend responsive to the physiological signal and providing the pulse waveform in a first display view. Other steps include presenting at least a portion of the data trend in a second display view, selecting a first icon accessible from the first display view to switch to the second display view, and selecting a second icon accessible from the second display view to switch to the first display view.
Yet another aspect of a pulse oximetry user interface is a view means for presenting to a user data responsive to a physiological signal, a main menu means for choosing display related categories, and a category menu means for choosing display related parameters. The parameters determine the characteristic of the view means. The user interface also includes an icon means for designating the view means, accessing the menu means and altering the parameters. The interface further includes a soft key means for selecting the icon means.
For purposes of summarizing the invention, certain aspects, advantages and novel features of the invention have been described herein. Of course, it is to be understood that not necessarily all such aspects, advantages or features will be embodied in any particular embodiment of the invention.